What Are Epoxy Paints?
The hardest part of perfection is charging for it
Epoxy is just another five-letter word for money.”
This bold statement comes from Rick Anderson of Vancouver’s Best Painters, in Vancouver British Columbia and sums up his satisfaction with the little-understood product. Epoxy’s main claim to fame is longevity. It acts like a liquid plastic coating on everything from transistor parts to floors in theaters, shopping malls, garages, hospitals, and factories. The major use of two-part epoxy is to protect surfaces—typically floors— that see high traffic use daily. It is usually brushed and rolled on like paint. But, unlike latex or alkyd paint, which will last six months to a year, epoxy can last up to 10 years.
The reputation of epoxy paint has come a long way over the years. Anderson says it use to be that manufacturers could get away with just a drop of epoxy in a gallon of alkyd paint to be able to market it to the consumer as an epoxy product.
Most epoxies are not only chemically resistant but they have no VOCs to give off and are considered spark-proof. This makes epoxy ideal for chemical storage areas. They are also electrostatic dissipative floor coatings, meaning they resist static electric discharges, making them the floor coating of choice for computer chip manufacturing plants.
Epoxy costs can range from $40 per gallon to $200 per gallon, depending on the application. It can be tailored to almost any environmental application to prevent damage in extremely acidic or caustic industrial sites to the need for ultra-clean bio-hazard surfaces. Epoxies are made to be chemical resistant and can resist splashing of caustic materials or can be tailored for use inside a tank holding sulfuric acid.
The geeky explanation for epoxy or polyepoxide is that it is “a thermosdetting epoxide polymer, which cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener,” according to Wikipedia (a not-always reliable source for such information). All this means is that polymers chemically mix with hardness to produce heat and a hard plastic coating on the surface you are painting.
“Epoxies are seamless and thus easier to clean and they simply don’t allow germs and bacteria to breed,” says Rick Anderson
“Most of our products have steri-septic, anti-bacterial and anti-fungal agents built in for use in areas where cleanliness is a factor.”
Epoxy on concrete
Concrete is like a hard sponge and requires polyamines, an epoxy that flows smoothly like paint. Some epoxies, where corrosive resistance is the goal, are made for the steel. This is where the rare solvent polyarnide epoxy is used, but it will give off seriously toxic fumes.
But VOC epoxies are the exception today, not the norm. Today’s epoxy is considered a “green product” since it is made with 100 per cent solids. It has no VOC elements. Compare that to paint which is typically 60 per cent solids and 40 per cent solvents, which causes shrinkage of the product as it dries by evaporation.
Since most epoxies used in commercial applications are now solvent-free, they can be used without masks in areas with ventilation. “The customer always gets his money’s worth when we put down an epoxy,” he says.
“It is a good-looking decorative product, clean, hard-wearing and it lasts for a decade or more. It can easily be recoated with some sanding. Paint on cement, on the other hand, will fail in months or little more than a year.”
Water based epoxy
Water-based epoxy has one advantage over most epoxies, in that it can be used in damp areas, like mechanical rooms where there are typically lots of leaks. Since it is not as brittle as typical epoxies, water-based epoxy can be used on top of a rubber membrane base. It will expand and contract with the membrane and not break off. Water-based epoxies for residential DIY application are still better than paint for hardness and longevity, but still not as good as commercial-grade epoxies.
“They give up hardness and longevity for the convenience of more minutes in the pot and a three-hour working time,” Anderson says.
“It is false economy to save a few dollars per gallon for years on the floor. Why spend money on paint when you can go up a step or two and get a product that lasts for years?”
Epoxy is like liquid Durabond (a plaster mix). Once the two parts of epoxy are mixed, the clock is ticking. There is no stopping it from drying, so it has to be used immediately. The material will only stay workable for 20 minutes in the can and 90 minutes if it is poured out on the floor. It will dry to the touch in a few hours and cure in seven days.
Like most aspects of painting, preparation is the key in using epoxy, Anderson says.
The least preferred method of cleaning cement is washing it with muriatic acid. It leaves an invisible barrier on the surface, much like silicone, grease or oil—all things that prevent adhesion of any paint to cement.
“Mechanical methods are preferred, either by shot blasting or by abrasive sanding of the surface to remove barriers. Once clean, you will have to tear the concrete apart to remove the epoxy. It sticks better to concrete that it even does to itself.” Anderson says.
To prove the point, according to Anderson most epoxies have a compressive strength of 9,425 psi, while concrete comes in at 3,600 psi. Epoxy is three times stronger than cement once dried.
Epoxy fillers are also a two-part product, as the putty has to be used once mixed. Regular paint can be painted over an epoxy primer, but epoxies shouldn’t be used on top of paints of any kind. The heat from the chemical reaction will soften the paint. Since epoxy grips so tightly, what little shrinkage there is will pull the paint off the surface easily. However, epoxy is not recommended in damp areas or in direct sunlight. Humidity under the epoxy coating will have the same effect as it does on regular paint, forming a barrier under the surface and eventually causing the paint to let go. UV light will discolor epoxies, but will not otherwise damage it. It may not look pretty, but in areas where the surface must be protected outside, epoxy is still better than exterior paint.